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          最近的四道题
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        <p><a target="_blank" rel="noopener" href="http://codeforces.com/contest/380/problem/C">http://codeforces.com/contest/380/problem/C</a> <span id="more"></span></p>
<blockquote>
<p>题目大意：给定一个括号序列，给出一个询问<span class="math inline">\(l\)</span>和<span class="math inline">\(r\)</span>，回答<span class="math inline">\(l\)</span>到<span class="math inline">\(r\)</span>这个范围内，最长的合法子序列是多长</p>
</blockquote>
<p>经过观察，这个题目符合区间合并性。 <span class="math display">\[w[Total].len=w[Left].len+w[Right].len+min(w[Left].open+w[Right].closed)\]</span> <span class="math display">\[w[Total].open=w[Left].open+w[Right].open-min(w[Left].open+w[Right].closed)\]</span> <span class="math display">\[w[Total].closed=w[Left].closed+w[Right].closed-min(w[Left].open+w[Right].closed)\]</span> 这样就可以用线段树来维护。</p>
<figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span><span class="meta-string">&lt;bits/stdc++.h&gt;</span></span></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> std;</span><br><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">node</span>&#123;</span></span><br><span class="line">	<span class="keyword">int</span> z,y,len;</span><br><span class="line">&#125;;</span><br><span class="line"><span class="keyword">char</span> s[<span class="number">1000010</span>];</span><br><span class="line"><span class="keyword">int</span> n,m;</span><br><span class="line">node w[<span class="number">4000010</span>];</span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">build</span><span class="params">(<span class="keyword">int</span> o,<span class="keyword">int</span> l,<span class="keyword">int</span> r)</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">	<span class="keyword">if</span>(l==r)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="comment">//cout&lt;&lt;l&lt;&lt;&quot; &quot;&lt;&lt;s[l]&lt;&lt;&quot; &quot;&lt;&lt;o&lt;&lt;endl;</span></span><br><span class="line">		<span class="keyword">if</span>(s[l]==<span class="string">&#x27;(&#x27;</span>) w[o].z=<span class="number">1</span>;</span><br><span class="line">		<span class="keyword">else</span> w[o].y=<span class="number">1</span>;</span><br><span class="line">		w[o].len=<span class="number">0</span>;</span><br><span class="line">		<span class="keyword">return</span>;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">int</span> m=(l+r)/<span class="number">2</span>;</span><br><span class="line">	node zz; node yy;</span><br><span class="line">	<span class="built_in">build</span>(o*<span class="number">2</span>,l,m);</span><br><span class="line">	zz=w[o*<span class="number">2</span>];</span><br><span class="line">	<span class="built_in">build</span>(o*<span class="number">2</span>+<span class="number">1</span>,m+<span class="number">1</span>,r);</span><br><span class="line">	yy=w[o*<span class="number">2</span>+<span class="number">1</span>];</span><br><span class="line">	w[o].len=w[o*<span class="number">2</span>].len+w[o*<span class="number">2</span>+<span class="number">1</span>].len+<span class="built_in">min</span>(w[o*<span class="number">2</span>].z,w[o*<span class="number">2</span>+<span class="number">1</span>].y)*<span class="number">2</span>;</span><br><span class="line">	w[o].z=w[o*<span class="number">2</span>].z+w[o*<span class="number">2</span>+<span class="number">1</span>].z-<span class="built_in">min</span>(w[o*<span class="number">2</span>].z,w[o*<span class="number">2</span>+<span class="number">1</span>].y);</span><br><span class="line">	w[o].y=w[o*<span class="number">2</span>].y+w[o*<span class="number">2</span>+<span class="number">1</span>].y-<span class="built_in">min</span>(w[o*<span class="number">2</span>].z,w[o*<span class="number">2</span>+<span class="number">1</span>].y);</span><br><span class="line">&#125;</span><br><span class="line">node ans;</span><br><span class="line"><span class="keyword">int</span> a,b;</span><br><span class="line"><span class="function">node <span class="title">query</span><span class="params">(<span class="keyword">int</span> o,<span class="keyword">int</span> L,<span class="keyword">int</span> R)</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">	<span class="keyword">int</span> M=L+(R-L)/<span class="number">2</span>;</span><br><span class="line">	node ans;</span><br><span class="line">	<span class="keyword">if</span>(a&lt;=L&amp;&amp;R&lt;=b)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="comment">//cout&lt;&lt;a&lt;&lt;&quot; &quot;&lt;&lt;b&lt;&lt;&quot; &quot;&lt;&lt;o&lt;&lt;&quot; &quot;&lt;&lt;w[o].z&lt;&lt;&quot; &quot;&lt;&lt;w[o].y&lt;&lt;&quot; &quot;&lt;&lt;w[o].len&lt;&lt;endl;</span></span><br><span class="line">		<span class="keyword">return</span> w[o];</span><br><span class="line">	&#125;</span><br><span class="line">	node zz;</span><br><span class="line">	node yy;</span><br><span class="line">	ans.len=<span class="number">0</span>;ans.z=<span class="number">0</span>;ans.y=<span class="number">0</span>;</span><br><span class="line">	zz.len=<span class="number">0</span>;zz.z=<span class="number">0</span>;zz.y=<span class="number">0</span>;</span><br><span class="line">	yy.len=<span class="number">0</span>;yy.z=<span class="number">0</span>;yy.y=<span class="number">0</span>;</span><br><span class="line">	<span class="keyword">if</span>(a&lt;=M)</span><br><span class="line">	&#123;</span><br><span class="line">		zz=<span class="built_in">query</span>(o*<span class="number">2</span>,L,M);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">if</span>(M&lt;b)</span><br><span class="line">	&#123;</span><br><span class="line">		yy=<span class="built_in">query</span>(o*<span class="number">2</span>+<span class="number">1</span>,M+<span class="number">1</span>,R);</span><br><span class="line">	&#125;</span><br><span class="line">	ans.len=zz.len+yy.len+<span class="built_in">min</span>(zz.z,yy.y)*<span class="number">2</span>;</span><br><span class="line">	ans.z=zz.z+yy.z-<span class="built_in">min</span>(zz.z,yy.y);</span><br><span class="line">	ans.y=zz.y+yy.y-<span class="built_in">min</span>(zz.z,yy.y);</span><br><span class="line">	<span class="keyword">return</span> ans;</span><br><span class="line">&#125;</span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">	<span class="built_in">scanf</span>(<span class="string">&quot;%s&quot;</span>,s+<span class="number">1</span>);</span><br><span class="line">	n=<span class="built_in">strlen</span>(s+<span class="number">1</span>);</span><br><span class="line">	<span class="built_in">build</span>(<span class="number">1</span>,<span class="number">1</span>,n);</span><br><span class="line">	<span class="built_in">scanf</span>(<span class="string">&quot;%d&quot;</span>,&amp;m);</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">1</span>;i&lt;=m;i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">scanf</span>(<span class="string">&quot;%d%d&quot;</span>,&amp;a,&amp;b);</span><br><span class="line">		ans=<span class="built_in">query</span>(<span class="number">1</span>,<span class="number">1</span>,n);</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot;%d\n&quot;</span>,ans.len);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p><a target="_blank" rel="noopener" href="http://codeforces.com/contest/383/problem/C">http://codeforces.com/contest/383/problem/C</a></p>
<blockquote>
<p>题目大意：对一个节点加一个值<span class="math inline">\(val\)</span>，其每一个子节点都要减去值<span class="math inline">\(val\)</span>，向下不断传导，直到没有子节点。给出修改和查询，输出查询的答案。</p>
</blockquote>
<p>根据层数的奇偶性，对dfs序建立两个树状数组（或者线段树），因为dfs序的子树处于同一区间，所以就是区间修改，单点查询。</p>
<figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span><span class="meta-string">&lt;bits/stdc++.h&gt;</span></span></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> std;</span><br><span class="line"><span class="class"><span class="keyword">class</span> <span class="title">TreeDiv</span>&#123;</span></span><br><span class="line"><span class="keyword">public</span>:</span><br><span class="line">	<span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">int</span> SIZE=<span class="number">200010</span>,BIAS=<span class="number">5</span>;</span><br><span class="line">	<span class="keyword">long</span> <span class="keyword">long</span> u[<span class="number">2</span>][SIZE];</span><br><span class="line">	<span class="function"><span class="keyword">void</span> <span class="title">clear</span><span class="params">()</span></span>&#123;</span><br><span class="line">		<span class="built_in">memset</span>(u,<span class="number">0</span>,<span class="built_in"><span class="keyword">sizeof</span></span>(u));</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="function"><span class="keyword">void</span> <span class="title">modify</span><span class="params">(<span class="keyword">int</span> x,<span class="keyword">bool</span> f,<span class="keyword">long</span> <span class="keyword">long</span> v)</span></span>&#123;</span><br><span class="line">		<span class="keyword">for</span>(x+=BIAS;x&lt;SIZE;x+=x&amp;-x) u[f][x]+=v,u[!f][x]-=v;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="function"><span class="keyword">long</span> <span class="keyword">long</span> <span class="title">getsum</span><span class="params">(<span class="keyword">int</span> x,<span class="keyword">bool</span> f)</span></span>&#123;</span><br><span class="line">		<span class="keyword">long</span> <span class="keyword">long</span> s=<span class="number">0</span>;</span><br><span class="line">		<span class="keyword">for</span>(x+=BIAS;x;x-=x&amp;-x) s+=u[f][x];</span><br><span class="line">		<span class="keyword">return</span> s;</span><br><span class="line">	&#125;</span><br><span class="line">&#125; tr;</span><br><span class="line"><span class="keyword">int</span> v[<span class="number">200010</span>]=&#123;&#125;;</span><br><span class="line">vector&lt;<span class="keyword">int</span>&gt; e[<span class="number">200010</span>];</span><br><span class="line"><span class="keyword">int</span> n,m;</span><br><span class="line"><span class="keyword">int</span> a,b,c;</span><br><span class="line"><span class="keyword">int</span> l[<span class="number">200010</span>]=&#123;&#125;;</span><br><span class="line"><span class="keyword">int</span> r[<span class="number">200010</span>]=&#123;&#125;;</span><br><span class="line"><span class="keyword">bool</span> flag[<span class="number">200010</span>]=&#123;&#125;;</span><br><span class="line"><span class="keyword">int</span> deep;</span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">dfs</span><span class="params">(<span class="keyword">int</span> pr,<span class="keyword">int</span> x,<span class="keyword">bool</span> f)</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">	l[x]=++deep;</span><br><span class="line">	flag[x]=f;</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">0</span>;i&lt;e[x].<span class="built_in">size</span>();i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="keyword">if</span>(e[x][i]!=pr)</span><br><span class="line">		&#123;</span><br><span class="line">			<span class="built_in">dfs</span>(x,e[x][i],!f);</span><br><span class="line">		&#125;</span><br><span class="line">	&#125;</span><br><span class="line">	r[x]=deep;</span><br><span class="line">&#125;</span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">	<span class="built_in">scanf</span>(<span class="string">&quot;%d%d&quot;</span>,&amp;n,&amp;m);</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">1</span>;i&lt;=n;i++) <span class="built_in">scanf</span>(<span class="string">&quot;%d&quot;</span>,&amp;v[i]);</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">1</span>;i&lt;n;i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">scanf</span>(<span class="string">&quot;%d%d&quot;</span>,&amp;a,&amp;b);</span><br><span class="line">		e[a].<span class="built_in">push_back</span>(b);</span><br><span class="line">		e[b].<span class="built_in">push_back</span>(a);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">dfs</span>(<span class="number">0</span>,<span class="number">1</span>,<span class="number">0</span>);</span><br><span class="line">	tr.<span class="built_in">clear</span>();</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">1</span>;i&lt;=m;i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">scanf</span>(<span class="string">&quot;%d%d&quot;</span>,&amp;a,&amp;b);</span><br><span class="line">		<span class="keyword">if</span>(a==<span class="number">1</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			<span class="built_in">scanf</span>(<span class="string">&quot;%d&quot;</span>,&amp;c);</span><br><span class="line">			tr.<span class="built_in">modify</span>(l[b],flag[b],c);</span><br><span class="line">			tr.<span class="built_in">modify</span>(r[b]+<span class="number">1</span>,flag[b],-c);</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="keyword">else</span></span><br><span class="line">		&#123;</span><br><span class="line">			<span class="built_in">printf</span>(<span class="string">&quot;%d\n&quot;</span>,v[b]+tr.<span class="built_in">getsum</span>(l[b],flag[b]));</span><br><span class="line">		&#125;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p><a target="_blank" rel="noopener" href="http://codeforces.com/contest/414/problem/C">http://codeforces.com/contest/414/problem/C</a> 这题基本给定个一个归并的阶段。所以用归并排序求一下逆序数，然后翻转的话，就是整个层以及层以下都翻转（正序变成逆序，逆序变成正序），所以记录一下每一层的正序数、逆序数，暴力维护即可。</p>
<figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span><span class="meta-string">&lt;bits/stdc++.h&gt;</span></span></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> std;</span><br><span class="line"><span class="keyword">int</span> n,m;</span><br><span class="line"><span class="keyword">int</span> a[<span class="number">1100000</span>]=&#123;&#125;;</span><br><span class="line"><span class="keyword">int</span> tmp[<span class="number">1100000</span>]=&#123;&#125;;</span><br><span class="line"><span class="keyword">int</span> q;</span><br><span class="line"><span class="keyword">long</span> <span class="keyword">long</span> v[<span class="number">22</span>][<span class="number">3</span>]=&#123;&#125;;</span><br><span class="line"><span class="keyword">bool</span> bj[<span class="number">22</span>]=&#123;&#125;;</span><br><span class="line"><span class="function"><span class="keyword">long</span> <span class="keyword">long</span> <span class="title">ff</span><span class="params">(<span class="keyword">int</span> l,<span class="keyword">int</span> r,<span class="keyword">int</span> d)</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">	<span class="keyword">if</span>(d==<span class="number">0</span>) <span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">	<span class="keyword">int</span> ll,rr,mid=(l+r)/<span class="number">2</span>;</span><br><span class="line">	<span class="keyword">long</span> <span class="keyword">long</span> t,b,c;</span><br><span class="line">	t=<span class="number">0</span>,b=<span class="number">0</span>,c=<span class="number">0</span>;</span><br><span class="line">	v[d][<span class="number">2</span>]+=(c=<span class="built_in">ff</span>(l,mid,d<span class="number">-1</span>)+<span class="built_in">ff</span>(mid+<span class="number">1</span>,r,d<span class="number">-1</span>));</span><br><span class="line">	ll=l,rr=mid+<span class="number">1</span>;</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=l;i&lt;=r;i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="keyword">if</span>(ll&gt;mid||(rr&lt;=r&amp;&amp;a[rr]&lt;a[ll]))</span><br><span class="line">		&#123;</span><br><span class="line">			tmp[i]=a[rr++];</span><br><span class="line">			t+=mid-ll+<span class="number">1</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="keyword">else</span> tmp[i]=a[ll++];</span><br><span class="line">	&#125;</span><br><span class="line">	ll=l,rr=mid+<span class="number">1</span>;</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=l;i&lt;=r;i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="keyword">if</span>(rr&gt;r||(ll&lt;=mid&amp;&amp;a[ll]&lt;a[rr]))</span><br><span class="line">		&#123;</span><br><span class="line">			tmp[i]=a[ll++];</span><br><span class="line">			b+=r-rr+<span class="number">1</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="keyword">else</span> tmp[i]=a[rr++];</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=l;i&lt;=r;i++) a[i]=tmp[i];</span><br><span class="line">	v[d][<span class="number">0</span>]+=t;</span><br><span class="line">	v[d][<span class="number">1</span>]+=b;</span><br><span class="line">	v[d][<span class="number">2</span>]+=t;</span><br><span class="line">	<span class="keyword">return</span> t+c;</span><br><span class="line">&#125;</span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">	<span class="built_in">scanf</span>(<span class="string">&quot;%d&quot;</span>,&amp;n);</span><br><span class="line">	m=<span class="number">1</span>&lt;&lt;n;</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">1</span>;i&lt;=m;i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">scanf</span>(<span class="string">&quot;%d&quot;</span>,&amp;a[i]);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">ff</span>(<span class="number">1</span>,m,n);</span><br><span class="line">	<span class="built_in">scanf</span>(<span class="string">&quot;%d&quot;</span>,&amp;q);</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">1</span>;i&lt;=q;i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="keyword">int</span> x;</span><br><span class="line">		<span class="built_in">scanf</span>(<span class="string">&quot;%d&quot;</span>,&amp;x);</span><br><span class="line">		<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">1</span>;i&lt;=n;i++)</span><br><span class="line">		&#123;</span><br><span class="line">			<span class="keyword">if</span>(i&lt;=x) bj[i]=!bj[i];</span><br><span class="line">			v[i][<span class="number">2</span>]=v[i<span class="number">-1</span>][<span class="number">2</span>]+v[i][bj[i]];</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="built_in">printf</span>(<span class="string">&quot;%I64d\n&quot;</span>,v[n][<span class="number">2</span>]);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p><a target="_blank" rel="noopener" href="http://codeforces.com/contest/282/problem/E">http://codeforces.com/contest/282/problem/E</a> 用trie树进行贪心，第一次接触到这种东西</p>
<figure class="highlight cpp"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br><span class="line">52</span><br><span class="line">53</span><br><span class="line">54</span><br><span class="line">55</span><br><span class="line">56</span><br><span class="line">57</span><br><span class="line">58</span><br><span class="line">59</span><br><span class="line">60</span><br><span class="line">61</span><br><span class="line">62</span><br><span class="line">63</span><br><span class="line">64</span><br><span class="line">65</span><br><span class="line">66</span><br><span class="line">67</span><br><span class="line">68</span><br><span class="line">69</span><br><span class="line">70</span><br><span class="line">71</span><br><span class="line">72</span><br><span class="line">73</span><br><span class="line">74</span><br><span class="line">75</span><br><span class="line">76</span><br><span class="line">77</span><br><span class="line">78</span><br><span class="line">79</span><br><span class="line">80</span><br><span class="line">81</span><br><span class="line">82</span><br><span class="line">83</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">#<span class="meta-keyword">include</span><span class="meta-string">&lt;bits/stdc++.h&gt;</span></span></span><br><span class="line"><span class="keyword">using</span> <span class="keyword">namespace</span> std;</span><br><span class="line"><span class="keyword">int</span> n;</span><br><span class="line"><span class="keyword">long</span> <span class="keyword">long</span> a[<span class="number">100010</span>]=&#123;&#125;;</span><br><span class="line"><span class="keyword">long</span> <span class="keyword">long</span> p[<span class="number">100010</span>]=&#123;&#125;;</span><br><span class="line"><span class="keyword">long</span> <span class="keyword">long</span> h[<span class="number">100010</span>]=&#123;&#125;;</span><br><span class="line"><span class="keyword">int</span> tr[<span class="number">5000010</span>][<span class="number">2</span>]=&#123;&#125;;</span><br><span class="line"><span class="keyword">int</span> si=<span class="number">0</span>;</span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">cha</span><span class="params">(<span class="keyword">long</span> <span class="keyword">long</span> p)</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">	<span class="keyword">bool</span> e[<span class="number">50</span>]=&#123;&#125;;</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">45</span>;i&gt;=<span class="number">0</span>;i--)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="keyword">long</span> <span class="keyword">long</span> o=<span class="number">1ll</span>&lt;&lt;i;</span><br><span class="line">		<span class="keyword">if</span>(p&amp;o)</span><br><span class="line">		&#123;</span><br><span class="line">			e[i]=<span class="number">1</span>;</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="keyword">else</span> e[i]=<span class="number">0</span>;</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">int</span> t=<span class="number">0</span>;</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">45</span>;i&gt;=<span class="number">0</span>;i--)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="keyword">if</span>(tr[t][e[i]]==<span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			si++;</span><br><span class="line">			tr[t][e[i]]=si;</span><br><span class="line">		&#125;</span><br><span class="line">		t=tr[t][e[i]];</span><br><span class="line">	&#125;</span><br><span class="line">&#125;</span><br><span class="line"><span class="function"><span class="keyword">long</span> <span class="keyword">long</span> <span class="title">query</span><span class="params">(<span class="keyword">long</span> <span class="keyword">long</span> p)</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">	<span class="keyword">long</span> <span class="keyword">long</span> ans=<span class="number">0</span>;</span><br><span class="line">	<span class="keyword">int</span> t=<span class="number">0</span>;</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">45</span>;i&gt;=<span class="number">0</span>;i--)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="keyword">long</span> <span class="keyword">long</span> o=<span class="number">1ll</span>&lt;&lt;i;</span><br><span class="line">		<span class="keyword">if</span>((p&amp;o)&amp;&amp;tr[t][<span class="number">0</span>])</span><br><span class="line">		&#123;</span><br><span class="line">			<span class="comment">//cout&lt;&lt;p&lt;&lt;&quot; &quot;&lt;&lt;o&lt;&lt;&quot; &quot;&lt;&lt;t&lt;&lt;&quot; *****&quot;&lt;&lt;endl;</span></span><br><span class="line">			</span><br><span class="line">			ans+=o;</span><br><span class="line">			t=tr[t][<span class="number">0</span>];</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="keyword">else</span> <span class="keyword">if</span>(tr[t][<span class="number">1</span>]==<span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			t=tr[t][<span class="number">0</span>];</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="keyword">else</span> <span class="keyword">if</span>((p&amp;o)==<span class="number">0</span>)</span><br><span class="line">		&#123;</span><br><span class="line">			<span class="comment">//cout&lt;&lt;p&lt;&lt;&quot; &quot;&lt;&lt;o&lt;&lt;&quot; &quot;&lt;&lt;&quot; _____&quot;&lt;&lt;endl;</span></span><br><span class="line">			ans+=o;</span><br><span class="line">			t=tr[t][<span class="number">1</span>];</span><br><span class="line">		&#125;</span><br><span class="line">		<span class="keyword">else</span> t=tr[t][<span class="number">1</span>];</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">return</span> ans;</span><br><span class="line">&#125;</span><br><span class="line"><span class="function"><span class="keyword">int</span> <span class="title">main</span><span class="params">()</span></span></span><br><span class="line"><span class="function"></span>&#123;</span><br><span class="line">	<span class="built_in">scanf</span>(<span class="string">&quot;%d&quot;</span>,&amp;n);</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">1</span>;i&lt;=n;i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">scanf</span>(<span class="string">&quot;%I64d&quot;</span>,&amp;a[i]);</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">1</span>;i&lt;=n;i++)</span><br><span class="line">	&#123;</span><br><span class="line">		p[i]=p[i<span class="number">-1</span>]^a[i];</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=n;i&gt;=<span class="number">1</span>;i--)</span><br><span class="line">	&#123;</span><br><span class="line">		h[i]=h[i+<span class="number">1</span>]^a[i];</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="keyword">long</span> <span class="keyword">long</span> ans=<span class="number">0</span>;</span><br><span class="line">	<span class="keyword">for</span>(<span class="keyword">int</span> i=<span class="number">1</span>;i&lt;=n+<span class="number">1</span>;i++)</span><br><span class="line">	&#123;</span><br><span class="line">		<span class="built_in">cha</span>(p[i<span class="number">-1</span>]);</span><br><span class="line">		ans=<span class="built_in">max</span>(ans,<span class="built_in">query</span>(h[i]));</span><br><span class="line">	&#125;</span><br><span class="line">	<span class="built_in">printf</span>(<span class="string">&quot;%I64d\n&quot;</span>,ans);</span><br><span class="line">	<span class="keyword">return</span> <span class="number">0</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

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